Reciprocating wire feed welding system and method

ABSTRACT

A consumable filler metal delivery system includes a reciprocating wire feeding gear assembly configured to move a wire forward and backward with a net forward motion and a motor configured to drive the reciprocating wire feeding gear assembly, wherein the motor is configured to rotate only in one direction during operation of the consumable filler metal delivery system.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and benefit of U.S. ProvisionalPatent Application No. 62/271,983, entitled “RECIPROCATING WIRE FEEDWELDING SYSTEM AND METHOD,” filed Dec. 28, 2015, which is hereinincorporated by reference in its entirety.

BACKGROUND

The present disclosure relates generally to welding systems, and moreparticularly to a reciprocating wire feed system configured to enablecontrolled short circuits between a welding wire and an advancing weld.

A wide range of welding systems and welding control regimes have beenimplemented for various purposes. In continuous welding processes withconsumable electrode, gas metal arc welding (GMAW), and morespecifically, metal inert gas (MIG) or metal active gas (MAG) techniques(collectively called GMAW) allow for formation of a continuing weld beadby feeding welding wire electrode shielded by gas (typically an inertgas or gas containing inert agents or active gas such as CO₂ or oxygen)from a welding torch. One variation of GMAW is Flux Cored Arc Welding(FCAW) with a consumable electrode containing flux in the coresurrounded by metal sheath. In such applications, the welding can bedone with or without shielding gas. Another welding process is submergedarc welding (SAW), or sub-arc for short, where shielding is accomplishedby solid powder flux instead of gas, and the arc is buried under theflux bed. Another welding process decouples wire feed from the heatsource, where the heat source may be laser, electron beam, plasma orTIG, and the wire (e.g., consumable electrode) may be cold or “hot”(e.g., pre-heated) before entering (e.g., being deposited) into themelted puddle on the workpiece created by the heat source. Electricalpower is applied to the welding wire and a circuit is completed throughthe workpiece to sustain an arc that melts the wire and the workpiece toform the desired weld.

Advanced forms of welding with consumable electrode can be based uponcontrolled short circuits between the wire electrode and the advancingweld puddle formed from melted metal of the workpieces and the wireelectrode. One method of controlling short circuit behavior is weldingcurrent reduction during short-to-arc and arc-to-short transitions viacurrent regulation or a secondary switch in the welding power supply.

In other applications, the controlled short circuits may be created by areciprocating wire feed system configured to oscillating the weldingwire in and out of the advancing weld puddle. By oscillating the wire inand out of the weld puddle, liquid at the end of the welding wire may bedipped into the puddle mechanically and detached form the welding wirewhen the wire is pulled out of the puddle, thereby accomplishing a“controlled short circuit” effect. Typically, mechanical motion of thewire is slow. To achieve desired higher deposition and faster weldingtravel speed, the wire must move bi-directionally in excess of 1000inches per minute and at a rate in excess of 100 Hz at 100% duty cycle.Traditional reciprocating wire feed systems use a bi-directional motor,and bi-directional motors typically have high torque requirements toovercome the inertia of the motor, the drive rolls and/or gears.Bi-directional motors may have limitations on the reciprocatingfrequency (which in turn imposes limitation on wire feed and travelspeeds and productivity), and may be susceptible to overheating, and/ormay be oversized, which may cause weld joint accessibility issues.

BRIEF DESCRIPTION

In one embodiment, a reciprocating welding wire feed system includes afirst drive roll comprising a first set of protrusions extendingradially outward from the first drive roll and configured to drive awelding wire in a first linear direction and a second drive rolldisposed adjacent to the first drive roll, wherein the second drive rollcomprises a second set of protrusions extending radially outward fromthe second drive roll and configured to drive the welding wire in asecond linear direction opposite the first direction, wherein the firstdrive roll and the second drive rolls do not contact the welding wiresimultaneously.

In another embodiment, a reciprocating welding wire feed system includesa first drive roll configured to contact a welding wire, a second driveroll disposed adjacent to the first drive roll on a same side of thewelding wire, wherein the second drive roll is configured to contact thewelding wire, a first expandable roll disposed opposite the first driveroll relative to the welding wire, and a second expandable roll disposedopposite the second drive roll relative to the welding wire, wherein thefirst expandable roll is configured to expand radially upon applicationof an electrical signal to the first expandable roll, and the secondexpandable roll is configured to expand radially upon application of theelectrical signal to the second expandable roll.

In a further embodiment, a method includes driving rotation of a gear ofa reciprocating welding wire feed system with a motor rotating in onlyone rotational direction, feeding a welding wire through thereciprocating welding wire feed system in a first linear direction bydriving the gear in the one rotational direction, and retracting thewelding wire through the reciprocating welding wire feed system in asecond linear direction opposite the first linear direction by drivingthe gear in the one rotational direction.

In another embodiment, a consumable filler metal delivery systemincludes a reciprocating wire feeding gear assembly configured to move awire forward and backward with a net forward motion and a motorconfigured to drive the reciprocating wire feeding gear assembly,wherein the motor is configured to rotate only in one direction duringoperation of the consumable filler metal delivery system.

DRAWINGS

FIG. 1 is a diagrammatical representation of a welding system having areciprocating wire feed system, in accordance with an embodiment of thepresent disclosure;

FIG. 2 is a perspective view of an embodiment of a reciprocating wirefeed system having toothed drive rolls, in accordance with an embodimentof the present disclosure;

FIG. 3 is a perspective view of an embodiment of a reciprocating wirefeed system having toothed drive rolls, in accordance with an embodimentof the present disclosure;

FIG. 4 is a perspective view of an embodiment of a reciprocating wirefeed system having expandable drive rolls, in accordance with anembodiment of the present disclosure;

FIG. 5 is a perspective view of an embodiment of a reciprocating wirefeed system having expandable drive rolls, in accordance with anembodiment of the present disclosure;

FIG. 6A is an exploded perspective view of an embodiment of areciprocating wire feed system having a planetary gear system, inaccordance with an embodiment of the present disclosure;

FIG. 6B is an assembled perspective view of an embodiment of areciprocating wire feed system having a planetary gear system, inaccordance with an embodiment of the present disclosure;

FIG. 7 is a schematic of an embodiment of a reciprocating wire feedsystem having a sensor system, in accordance with an embodiment of thepresent disclosure; and

FIG. 8 is an assembled perspective view of an embodiment of areciprocating wire feed system having a planetary gear system, inaccordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION

Embodiments of the present disclosure are directed toward areciprocating wire feed system for a welding system. More specifically,the disclosed embodiments include reciprocating wire feed systemsconfigured to be driven by a motor that rotates in one direction duringoperation while moving or driving a wire linearly with rapid changes ofdirection (e.g., forward and backward). For example, in one embodiment,the reciprocating wire feed system includes a toothed drive roll systemthat is driven by a motor rotating in only one direction and enables areciprocating or oscillating motion of a welding wire. In anotherembodiment, the reciprocating wire feed system includes an expanding andcontracting drive roll system that is driven by a motor rotating in onlyone direction and enables a reciprocating or oscillating motion of awelding wire. In a further embodiment, the reciprocating wire feedsystem includes a planetary gear assembly that is driven by a motorrotating in only one direction and enables a reciprocating oroscillating motion of a welding wire. Each of these embodiments arediscussed in further detail below.

As will be appreciated, the disclosed embodiments provide improvementsover traditional reciprocating wire feed systems (e.g., systems thatutilize bi-directional motors). For example, the disclosed reciprocatingwire feed systems utilize a motor rotating in only one direction thatmay be cheaper, smaller, lighter in weight, less susceptible tooverheating, may use less torque than bi-directional motors, and mayenable a change of wire direction at higher frequencies. Additionally,the disclosed embodiments may be used in existing welding wire drivesystems with increased inertia to reverse wire direction. In otherwords, existing welding wire feed systems may be retrofitted to includethe disclosed reciprocating wire feed systems. The disclosed embodimentsmay also enable improvement in arc starting, reduction in spatter duringa welding operation, higher travel speeds, weld grain refinement, higherductility, and other improvements to the welding operation. While thepresent disclosure describes embodiments in a welding system context,the present techniques may also be used in other processes, such ascladding or brazing, that also use consumable electrodes (e.g., fillermetals). For example, the disclosed systems may be used to perform gasmetal arc welding, flux-cored arc welding, submerged arc welding,tungsten inert gas welding with hot wire/cold wire, laser welding,plasma welding, cladding, brazing process, a multi-wire process, or anycombination thereof.

It should be noted that the term “wire feeder” used herein includes anysystem (e.g., mechanism) configured to feed a wire. For example, thewire feeder may be a standalone system or a component of another system.In one implementation, the wire feeder (e.g., wire feeding mechanism)may be a part (e.g., an integral component of a welding torch. As such,the wire feeder may only be a few feet away from a contact tip (e.g.,3-5 feet) of the torch. In another embodiment, the wire feeder is aseparately packaged object that the welding torch plugs into. Forexample, the wire feeder may be physically mounted on a robot arm.

Turning now to the drawings, and referring first to FIG. 1, an exemplarywelding system is illustrated as including a power supply 10 and a wirefeeder 12 coupled to one another via conductors or conduits 14. Forexample, the welding system may be an automated welding system that isautomated robotically. In the illustrated embodiment, the power supply10 is separate from the wire feeder 12, such that the wire feeder 12 maybe positioned at some distance from the power supply 10 near a weldinglocation. However, it should be understood that the wire feeder 12, insome implementations, may be integral with the power supply 10. In suchcases, the conduits 14, except for the ground conduit, would be internalto the system. In embodiments in which the wire feeder 12 is separatefrom the power supply 10, terminals are typically provided on the powersupply 10 and on the wire feeder 12 to allow the conductors or conduits14 to be coupled to the systems so as to allow for power and gas to beprovided to the wire feeder 12 from the power supply 10, and to allowdata to be exchanged between the two devices.

The system is designed to provide wire, power and shielding gas to awelding torch 16. As will be appreciated by those skilled in the art,the welding torch 16 may be of many different types, and typicallyallows for the feed of a welding wire and gas to a location adjacent toa workpiece 18 where a weld is to be formed to join two or more piecesof metal. A second conductor 14 is typically run to the weldingworkpiece 18 so as to complete an electrical circuit between the powersupply 10 and the workpiece 18.

The system is designed to allow for weld parameter settings to beselected by the operator, particularly via an operator interface 20provided on the power supply 10. The operator interface 20 willtypically be incorporated into a front faceplate of the power supply 10,and may allow for selection of settings such as the weld process, thetype of wire to be used, voltage and current settings, and so forth. Inparticular, the system is designed to allow for welding with consumableelectrode, such as various steels, aluminums, or other welding wire thatis channeled through the torch. These weld settings are communicated tocontrol circuitry 22 within the power supply 10. The system may beparticularly adapted to implement welding regimes designed for certainelectrode types.

The control circuitry 22 operates to control generation of welding poweroutput that is applied to the welding wire for carrying out the desiredwelding operation. The control circuitry 22 is coupled to powerconversion circuitry 24. This power conversion circuitry 24 is adaptedto create the output power applied to the welding wire at the torch 16.Various power conversion circuits may be employed, including a boostconverter, a buck converter, inverters, phase controlledtransformer-rectifier circuits, and so forth. The configuration of suchcircuitry 24 may be of types generally known in the art in and ofitself. The power conversion circuitry 24 is coupled to a source ofelectrical power as indicated by arrow 26. The power 26 applied to thepower conversion circuitry 24 may originate in the power grid, althoughother sources of power may also be used, such as power generated by anengine-driven generator, batteries, fuel cells or other alternativesources. Finally, the power supply 10 illustrated in FIG. 1 includesinterface circuitry 28 designed to allow the control circuitry 22 toexchange signals with the wire feeder 12.

The wire feeder 12 includes complementary interface circuitry 30 that iscoupled to the interface circuitry 28. In some embodiments, multi-pininterfaces may be provided on both components and a multi-conductorcable run between the interface circuitries 28, 30 to allow for suchinformation as wire feed speeds, processes, selected currents, voltagesor power levels, and so forth to be set on either the power supply 10,the wire feeder 12, or both.

The wire feeder 12 also includes control circuitry 32 coupled to theinterface circuitry 30. The control circuitry 32 allows for wire feedspeeds to be controlled in accordance with operator selections, andpermits these settings to be fed back to the power supply 10 via theinterface circuitry 30. The control circuitry 32 is coupled to anoperator interface 34 on the wire feeder 12 that allows selection of oneor more welding parameters, particularly wire feed speed. The operatorinterface 34 may also allow for selection of such weld parameters as theprocess, the type of wire utilized, current, voltage or power settings,and so forth. The control circuitry 32 is also coupled to gas controlvalving 36 which regulates the flow of shielding gas to the torch 16. Ingeneral, such gas is provided at the time of welding, and may be turnedon immediately preceding the weld and for a short time following theweld. The gas applied to the gas control valving 36 is often provided inthe form of pressurized bottles, as represented by reference numeral 38.In certain embodiments, the gas may be 100% CO₂ shielding gas.

The wire feeder 12 includes components for feeding wire to the weldingtorch 16 and thereby to the welding application, under the control ofcontrol circuitry 32. For example, one or more supplies (e.g., spool,box, etc.) of welding wire 42 are housed in the wire feeder 12. Weldingwire 42 is fed from the wire supply 40 and is progressively fed to thetorch 16. The wire supply 40 may be associated with a clutch 44 thatdisengages the wire supply 40 when wire 42 is to be fed to the torch 16.The clutch 44 may also be regulated to maintain a minimum friction levelto avoid free spinning of the wire supply 40. A feed motor 46 isprovided that engages with a reciprocating wire feed system 48 to pushwire 42 from the wire feeder 12 towards the workpiece 18. In particular,the reciprocating wire feed system 48 is configured to move the wire 42toward and away (e.g., two steps forward, one step backward for a netone step forward) from the welding torch 16 (and thus the workpiece 18)to enable a “controlled short circuit” operation of the torch 16. Forexample, a component (e.g., a roller) of the reciprocating wire feedsystem 48 may be mechanically coupled to the motor 46 and may be rotatedby the motor 46 to reciprocate and drive the wire 42 from the wirefeeder 12. Details of the reciprocating wire feed system 48 arediscussed in detail below. Finally, a tachometer or encoder or resolver50 may be provided for detecting the speed of the motor 46, a drive rolldriven by the motor 46, or other component of the reciprocating wirefeed system 48 so as to provide an indication of the actual wire 42 feedspeed. Signals from the tachometer 50 are fed back to the controlcircuitry 32, such as for closed loop feedback control or feedforwardcontrol. As described below, the system 48 may have drive rolls spinningin opposite directions. Accordingly, a logic “or” circuit may be usedcombine encoder A/B outputs of a forward drive roll and a rearward driveroll to produce combined pulse trains to encode actual wire 42 speed. Itis also possible to use an idler roll that is propelled by the wire 42motion as a wire speed sensor.

It should be noted that other system arrangements and input schemes mayalso be implemented. For example, the welding wire 42 may be fed from abulk storage container (e.g., a drum) or from one or more spools outsideof the wire feeder 12. Similarly, the wire 42 may be fed from a “spoolgun” in which a spool is mounted on or near the welding torch 16. Asnoted herein, the wire 42 feed speed settings may be input via theoperator input 34 on the wire feeder 12 or on the operator interface 20of the power supply 10, or both. Additionally, while the illustratedembodiment shows the reciprocating wire feed system 48 integrated withthe wire feeder 12, in other embodiments the reciprocating wire feedsystem 48 may be integrated with other another component (e.g., thewelding torch 16) or may be a stand-alone (e.g., modular) system.

Power from the power supply 10 is applied to the wire electrode,typically by means of a composite cable 52 (or separate cables) in aconventional manner for wire, gas, and welding current/power. Similarly,shielding gas is fed through the wire feeder 12 and the composite cable52. During welding operations, the wire 42 is advanced through thecomposite cable 52 towards the torch 16. Upon receiving command from aweld sequence controller (e.g., inside the control circuitry 22 insidepower source 10), gas flow is begun, wire 42 is advanced, power isapplied to the welding cable 52 and through the torch 16 to theadvancing welding wire 42. Finally, a workpiece ground cable and clamp56 allow for closing an electrical circuit from the power supply 10through the welding torch 16, the electrode (wire 42), the arc, and theworkpiece 18 back to the power conversion circuitry 24.

Although the motor 46, reciprocating wire feed system 48, and tachometer50 shown inside wire feeder 12 in FIG. 1, these elements may be separatecomponents or may be components of another system. For example, themotor 46, reciprocating wire feed system 48, and tachometer 50 may bepackaged inside torch 16. In some embodiments, there may be one or tworeciprocating wire feeding mechanisms 48 for wire delivery. When thefrictional resistance of wire to liner is high or spool inertia must beovercome, a dual feeder arrangement may be used. In such an embodiment,one motor 46 in the wire feeder 12 may be considered the “assist feeder”to push wire 42 thru conduit from the wire supply 40 to the torch 16,while another motor 46 in the torch 16 operates the reciprocating wirefeed system 48 inside the torch 16. The two motors 48 may besynchronized or asynchronous where the assist feeder may be put in aconstant torque mode.

FIGS. 2 and 3 are perspective views of an embodiment of thereciprocating wire feed system 48, which may be integrated with the wirefeeder 12 shown in FIG. 1. In the illustrated embodiment, thereciprocating wire feed system 48 includes a toothed drive roll system70. For the purpose of this disclosure, a “drive roll” may be consideredan actively driven roll from a wire engagement perspective, rather thanfrom motor engagement perspective. This distinction is importantbecause, in a conventional wire feeder, a drive roll may be activelydriven from a wire engagement and a motor perspective. In the presentdisclosure, multiple driven rolls may engage a wire in differentdirections but may all be powered off the same motor shaft.

The toothed drive roll system 70 includes a first drive roll 72 and asecond drive roll 74. The toothed drive roll system 70 also includes afirst idler roll 76 and a second idler roll 78. As shown, the first andsecond drive rolls 72 and 74 are disposed adjacent to one another on afirst side 80 of the wire 42, and the first and second idler rolls 76and 78 are disposed adjacent to one another on a second side 82 of thewire 42. In other embodiments, the first and second drive rolls 72 and74 may not be opposite the first and second idler rolls 76 and 78relative to the wire 42. For example, the first and second drive rolls72 and 74 and the first and second idler rolls 76 and 78 may be on thesame side of the wire 42.

In the illustrated embodiment, the first drive roll 72 and the firstidler roll 76 are disposed opposite one another about the wire 42, andthe second drive roll 74 and the second idler roll 78 are disposedopposite one another about the wire 42. Thus, the wire 42 extendsthrough the reciprocating wire feed system 48 between the first driveroll 72 and the first idler roll 76 and then between the second driveroll 74 and the second idler roll 78. In the manner described below, thereciprocating wire feed system 48 shown in FIGS. 2 and 3 operates tooscillate or reciprocate the welding wire 42 toward the torch 16 (e.g.,in a direction 84) and away from the torch 16 (e.g., in a direction 86).

As discussed above, the motor 46 may drive the reciprocating wire feedsystem 48. In the illustrated embodiment, the first and second driverolls 72 and 74 are coupled to one another via respective gears (e.g., afirst gear 88 and a second gear 90). Thus, the motor 46 may be coupledto the first gear 88 or the second gear 90 and thereby drive both thefirst drive roll 72 and the second drive roll 74 simultaneously. Thefirst and second idler rolls 76 and 78 may not be coupled to the motor46, but in other embodiments, the first and second idler rolls 76 and 78may also be driven by a motor, thereby also becoming driven rolls.

As mentioned above, the first and second drive rolls 72 and 74 aresimultaneously driven by the motor 46 (i.e., via coupling of the firstand second gears 88 and 90), but the first drive roll 72 and the seconddrive roll 74 are configured such that only one of the first and seconddrive rolls 72 and 74 is driving the welding wire 42 at a given time.Specifically, each of the first and second drive rolls 72 and 74 includeprotruding portions 92 extending from a respective base outer diameter94 of the first and second drive rolls 72 and 74, and spanning an entirewidth of the respective drive roll 72, 74. Each protruding portion 92 ofthe first and second drive rolls 72 and 74 has a trough 96 that isformed circumferentially along the protruding portion 92 which mayengage with the welding wire 42 intermittently as the first and seconddrive rolls 72 and 74 are driven by the motor 46. In certainembodiments, the troughs 96 may have a U-shape, a V-shape, or othersuitable shape that reliably hugs and grips the wire 42 withoutslipping, deforming or shaving the wire 42. Additionally, in certainembodiments, the troughs 96 may have a surface treatment, such asknurling. As shown, the first and second idler rolls 76 and 78 alsoinclude troughs 96, which may extend completely around a respectivecircumference 97 of the first and second idler rolls 76 and 78.

In certain embodiments, the protruding portions 92 of the first driveroll 72 are spaced equidistantly about a circumference 98 of the firstdrive roll 72, and the protruding portions 92 of the second drive roll74 are spaced equidistantly about a circumference 100 of the seconddrive roll 74. Additionally, the protruding portions 92 of the firstdrive roll 72 are staggered or “out of phase” relative to the protrudingportions 92 of the second drive roll 74. As a result, when one of theprotruding portions 92 of the second drive roll 74 is in contact withthe welding wire 42, as shown in FIG. 2, no protruding portion 92 of thefirst drive roll 72 is in contact with the welding wire 42. Instead,when one of the protruding portions 92 of the second drive roll 74 is incontact with the welding wire 42, a recessed portion 102 between twoprotruding portions 92 of the first drive roll 72 is exposed to thewelding wire 42 and disengage roll 72 from wire 42. Similarly, when oneof the protruding portions 92 of the first drive roll 72 is in contactwith the welding wire 42, as shown in FIG. 3, no protruding portion 92of the second drive roll 74 is in contact with the welding wire 42.Instead, when one of the protruding portions 92 of the first drive roll72 is in contact with the welding wire 42, a recessed portion 104between two protruding portions 92 of the second drive roll 74 isexposed to the welding wire 42 and disengage roll 74 from wire 42. Inthis way, the first and second drive rolls 72 and 74 are configured suchthat only one of the drive rolls 72 and 74 is contacting the weldingwire 42 at a given point in time.

As mentioned above, the first and second drive rolls 72 and 74 arecoupled to one another via the first and second gears 88 and 90. Morespecifically, the first and second gears 88 and 90 are coupled to oneanother such that rotation of the first gear 88 and a direction 106drives rotation of the second gear 90 in a direction 108, which isopposite the direction 106. Thus, as indicated by arrows 112 and 114,the first and second drive rolls 72 and 74 are driven in oppositedirections in a synchronized manner.

When the one of the protrusions 92 of the second drive roll 74 engageswith the welding wire 42, the reciprocating wire feed system 48 drivesthe welding wire 42 in the direction 84 (e.g., toward the torch 16), asshown in FIG. 2. When the second drive roll 74 is driving the weldingwire 42 in the direction 84, the second idler roll 78 may also rotate(e.g., in a direction 116). As the first and second drive rolls 72 and74 continue to rotate, the protruding portions 92 of the second driveroll 74 will lose contact with the welding wire 42, and one of theprotruding portions 92 of the first drive roll 72 will make contact withthe welding wire 42, as shown in FIG. 3. When one of the protrudingportions 92 of the first drive roll 72, which is rotating in thedirection 112 opposite the direction 114 of the second drive roll 74,makes contact with the welding wire 42 and drives the welding wire 42 inthe direction 86 (e.g., away from the torch 16). When the first driveroll 72 is driving the welding wire 42 in the direction 86, the firstidler roll 76 may also rotate (e.g., in a direction 118).

As the first and second drive rolls 72 and 74 continuously rotate, therespective protruding portions 92 of the first and second drive rolls 72and 74 may make alternating contact with the welding wire 42 and drivethe welding wire 42 toward and away from the welding torch 16 in themanner described above. As a result, the reciprocating wire feed system48 creates an oscillating or reciprocating movement of the welding wire42.

Moreover, in certain embodiments, the protruding portions 92 of thesecond drive roll 74 each have and arc length 120 that is greater thanan arc length 122 of each of the protruding portions 92 of the firstdrive roll 72. As a result, the protruding portions 92 of the seconddrive roll 74 stay in contact with the welding wire 42 longer than theprotruding portions 92 of the first drive roll 72 when the reciprocatingwire feed system 48 is operating. The greater arc lengths 120 of theprotruding portions 92 of the second drive roll 74 cause thereciprocating wire feed system 48 to drive the welding wire 42 fartherin the direction 84 than the direction 86 when the reciprocating wirefeed system 48 is operating. In other words, the greater arc lengths 120of the protruding portions 92 of the second drive roll 74, compared tothe shorter arc lengths 122 of the protruding portions 92 of the firstdrive roll 72 enable the reciprocating wire feed system 48 to drive thewelding wire 42 in a net forward motion with reciprocating motion,figuratively speaking, “two steps toward” the torch 16 and “one stepback” from the welding torch 16, as mentioned above. In certainembodiments, the arc lengths 120 may be approximately 1.1, 1.2, 1.3,1.4, 1.5, 2, 3, 4, 5 or more times greater than the arc lengths 122. Incertain embodiments, the arc lengths 120 and 122 may be sized such thatno protruding portions 92 contacts the welding wire 42 for a briefmoment (e.g., in between protruding portions 92 of the first drive roll72 and second drive roll 74 contacting the welding wire 42) to enable adelay or intermittent stop of the welding wire 42 movement. Thus, insuch embodiments, the sum of all arc lengths 120 and 122 of allprotruding portions 92 in the reciprocating wire feed system 48 may beless than 360 degrees.

The first and second drive rolls 72 and 74 and the first and secondidler rolls 76 and 78 may be formed from a variety of materials. Forexample, the first and second idler rolls 76 and 78 may be formed from alightweight material, such as aluminum, titanium, a ceramic, or apolymer, to reduce inertia in the starting and stopping of the first andsecond idler rolls 76 and 78. As the motor 46 drives (e.g., actively orpassively) the first and second drive rolls 72 and 74, the first andsecond drive rolls 72 and 74 may be formed from a heavier material, suchas steel. However, any suitable material may be used to form the firstand second drive rolls 72 and 74 and the first and second idler rolls 76and 78. The trough surfaces may be hardened by heat treatment orcarburizing to improve durability and wear resistance.

In the illustrated embodiments, the first and second drive rolls 72 and74 having the protruding portions 92 are on the same side of the weldingwire 42. However, in other embodiments, the first and second drive rolls72 and 74 having the protruding portions 92 may be on opposite sides ofthe welding wire 42. For example, in one embodiment, the positions ofthe second drive roll 74 and the second idler roll 78 shown in FIGS. 2and 3 may be reversed or switched. Thus, the first drive roll 72 and thesecond idler roll 78 may be adjacent to one another. In such anembodiment, the first and second drive rolls 72 and 74 may still begeared to one another, or the first and second drive rolls 72 and 74 maybe driven separately (e.g., by separate motors). In such an embodiment,the first and second drive rolls 72 and 74 may rotate in the samedirection instead of in directions opposite one another. In otherembodiments, the reciprocating wire feed system 48 may have otherconfigurations. For example, in another embodiment, the first and secondidler rolls 76 and 78 may also be driven by a motor, such that the firstand second idler rolls 76 and 78 are drive rolls (e.g., third and fourthdrive rolls). In such an embodiment, the first and second idler rolls 76and 78 may be geared to the first and/or second drive rolls 72 and/or74, or the first and second idler rolls 76 and 78 may be driven by oneor more separate motors. Further, in such an embodiment, the first andsecond idler rolls 76 and 78 may also include protrusions 92.

FIGS. 4 and 5 are perspective views of another embodiments of thereciprocating wire feed system 48, which may be integrated with the wirefeeder 12 shown in FIG. 1. In the illustrated embodiment, thereciprocating wire feed system 48 includes an expandable drive rollsystem 150. The expandable drive roll system 150 includes a first driveroll 152 and a second drive roll 154. The expandable drive roll system150 also includes a first expandable roll 156 and a second expandableroll 158. As shown, the first and second drive rolls 152 and 154 aredisposed adjacent to one another on the first side 80 of the wire 42,and the first and second expandable rolls 156 and 158 are disposedadjacent to one another on the second side 82 of the wire 42.Additionally, the first drive roll 152 and the first expandable roll 156are disposed opposite one another about the wire 42, and the seconddrive roll 154 and the second expandable roll 158 are disposed oppositeone another about the wire 42. Thus, the wire 42 extends through thereciprocating wire feed system 48 between the first drive roll 152 andthe first expandable roll 156 and then between the second drive roll 154and the second expandable roll 158. In the manner described below, thereciprocating wire feed system 48 shown in FIGS. 4 and 5 operates tooscillate or reciprocate the welding wire 42 toward the torch 16 (e.g.,in the direction 84) and away from the torch 16 (e.g., in the direction86).

As discussed above, the motor 46 may drive the reciprocating wire feedsystem 48. In the illustrated embodiment, the first and second driverolls 152 and 154 are coupled to one another via respective gears (e.g.,a first gear 160 and a second gear 162). Thus, the motor 46 may becoupled to the first gear 160 or the second gear 162 and thereby driveboth the first drive roll 152 and the second drive roll 154simultaneously. As similarly described above with reference to FIGS. 2and 3, the first and second drive rolls 152 and 154 are geared to oneanother such that the first and second drive rolls 152 and 154 aredriven to rotate in opposite directions, as indicated by arrows 164 and166.

As mentioned above, the welding wire 42 extends between the first driveroll 152 and the first expandable roll 156, and the welding wire 42 alsoextends between the second drive roll 154 and the second expandable roll158. As shown in FIGS. 4 and 5, each of the rolls 152, 154, 156, 158includes a trough (e.g., a circumferential trough) 168 through which thewelding wire 42 may pass as the welding wire 42 travels through thereciprocating wire feed system 48. The troughs 168 may be similar to thetroughs 96 discussed with reference to FIGS. 2 and 3.

In operation, the welding wire 42 may be engaged with either the firstdrive roll 152 and the first expandable roll 156 or the second driveroll 154 and the second expandable roll 158 at a given time. To enablethis operation, the first and second expandable rolls 156 and 158 areformed at least partially from a piezoelectric crystal, a piezo-ceramic,a PZT (e.g., lead zirconate titanate), or other material that may expandand contract with electrical stimulation. For example, in FIG. 4, anelectrical system (e.g., drive circuit or control system) 170 of thereciprocating wire feed system 48, controlled by control circuitry 32 ofFIG. 1, applies an electrical signal (e.g. drive potential) to thesecond expandable roll 158. As a result, the second expandable roll 158radially expands, as indicated by arrows 172, to engage the welding wire42 in conjunction with the second drive roll 154. The respective troughs168 of the second drive roll 154 and second expandable roll 158 capturethe welding wire 42. As the second drive roll 154 is rotated in thedirection 164, the welding wire 42 captured by the second drive roll 154and the second expandable roll 158 drive the welding wire 42 in thedirection 84 (e.g., toward the torch 16). At the same time, the secondexpandable roll 158, which is not driven by the motor 46 or the gears160 and 162, rotates in a direction 174 due to the friction createdbetween the second drive roll 154, the welding wire 42, and the secondexpandable roll 158.

When then second expandable roll 158 is actuated with an electricalsignal by the electrical system 170, the electrical system 170 may notapply an electrical signal to the first expandable roll 156 (enablingrelaxation or contraction of the first expandable roll 156) or apply anintermittent or continuous signal of opposite polarity to cause a fastercontraction of the first expandable roll 156. As a result, the firstexpandable roll 156 may be in a contracted (e.g., radially contracted)state, as indicated by arrows 176 in FIG. 4. Thus, the welding wire 42is not engaged by the first driver roll 152 and the first expandableroll 156.

To create the reciprocating or oscillating motion in the welding wire42, the electrical system 170 may suspend the application of anelectrical signal to the second expandable roll 158 and beginapplication of an electrical signal (e.g., control signal) to the firstexpandable roll 156. As a result, the second expandable roll 158 mayradially contract or relax, as indicated by arrows 180 in FIG. 5, andthe first expandable roll 156 may radially expand, as indicated byarrows 182 in FIG. 5. In this way, the respective troughs 168 of thefirst drive roll 152 and the first expandable roll 156 capture thewelding wire 42. As the first drive roll 152 is rotated in the direction166, the welding wire 42 captured by the first drive roll 152 and thefirst expandable roll 156 drive the welding wire 42 in the direction 86(e.g., away from the torch 16). At the same time, the first expandableroll 156, which is not driven by the motor 46 or the gears 160 and 162,rotates in a direction 184 due to the friction created between the firstdrive roll 152, the welding wire 42, and the first expandable roll 156.

As with the embodiment of the reciprocating wire feed system 48described above with reference to FIGS. 2 and 3, the embodiment of thereciprocating wire feed system 48 shown in FIGS. 4 and 5 may beconfigured to reciprocate the welding wire 42 with net forward motion,figuratively, “two steps forward, one step back.” To this end, theelectrical system 170 may be configured to apply electrical signals tothe first and second expandable rolls 156 and 158 for different lengthsof time or even a different polarity. For example, the electrical system170 may apply an electrical signal to the first expandable roll 156 fora first length of time (i.e., to force the welding wire 42 in thedirection 86 away from the torch 16), and the electrical system 170 maysubsequently apply an electrical signal (e.g., control signal) to thesecond expandable roll 158 for a second length of time that is twice aslong as the first length of time (i.e., to force the welding wire 42 inthe direction 84 toward the torch 16). This control scheme may berepeated to move the welding wire 42 towards the torch in areciprocating or oscillating fashion. In certain embodiments, theelectrical system 170 may pause or delay between sending electricalsignals to the first and second expandable rolls 156 and 158 toeffectuate a “stop” in the travel of the welding wire 42. In otherwords, when no electrical signal is applied to the first or secondexpandable rolls 156 and 158, both expandable rolls 156 and 158 may bein a radially contracted or relaxed state, and thus the welding wire 42may not be captured or engaged with the first drive roll 152 and thefirst expandable roll 156 or the second drive roll 154 and the secondexpandable roll 158.

As mentioned above, the first and second expandable rolls 156 and 158are formed from a piezoelectric crystal material, a piezo-ceramicmaterial, a PZT, or other material that enables expansion andcontraction of the first and second expandable rolls 156 and 158 uponapplication of an electrical signal. In some embodiments, the entirestructures of the first and second expandable rolls 156 and 158 areformed from the expandable material. However, in other embodiments, onlya portion (e.g., a central disk portion including the trough 168) of thefirst and second expandable rolls 156 and 158 is formed from theexpandable material.

FIG. 6A is an exploded perspective view of another embodiment of thereciprocating wire feed system 48, illustrating a planetary gear system200, and FIG. 6B is an assembled perspective view of the reciprocatingwire feed system 48, illustrating the planetary gear system 200. In theillustrated embodiment, the planetary gear system 200 includes a driveroll 202 and a pressure roll 204 (or an idler roll), which capture thewelding wire 42. The drive roll 202 is driven by the motor 46, which maybe coupled to the drive roll 202 via a shaft 206.

The planetary gear system 200 also includes a ring gear 208 and anenlarged planet gear 210 that fits within the ring gear 208. A centeringroller assembly 212 having rollers 214 is also disposed within the ringgear 208 that enable and ensure engagement between the planet gear 210and the ring gear 208. As will be appreciated, the planet gear 210orbits within the ring gear 208 as the planet gear 210 is driven by themotor 46 and the shaft 206. As the planet gear 210 is rotated within thering gear 208, the planet gear 210, and thus the drive roll 202, shiftsleft and right (e.g., in directions 216 and 218). However, the planetgear 210 and the drive roll 202 do not shift up and down (e.g., indirections 220 and 222) because the shaft 206, the planet gear 210, andthe drive roll 202 are restrained from moving in the directions 220 and222 by a shaft restraint 224 (e.g., vertical restraint), which may bepinned to a fixed structure at a joint 226 of the shaft restraint 224.However, the joint 226 is a pivotable joint that enables pivoting of theshaft restraint 224 in the directions 216 and 218.

As the planet gear 210 orbits within the ring gear 208, the ring gearmay move up and down in the directions 220 and 222, but horizontal orleft and right movement (e.g., in directions 216 and 218) of the ringgear 208 is restricted by a ring gear restraint 228 (e.g., horizontalrestraint). As with the shaft restraint 224, the ring gear restraint 228may be pivotably coupled to another structure of the reciprocating wirefeed system 48 at a joint 230.

As will be appreciated, the net motion of the welding wire 42 is a sumof the steady angular motion of the drive roll 202 and a cyclic lead orlag caused by the motion of a drive roll axis 232 in the directions 218and 216. The left and right motion of the drive roll 202 is transferredto the welding wire 42 due to the frictional engagement between thedrive roll 202, the pressure roll 204, and the welding wire 42. Indeed,the planetary gear system 200 enables left and right (e.g., directions216 and 218) movement of the drive roll 202 (and thus the wire 42) witha unidirectional rotational input from the motor 26. Thus, the weldingwire 42 may be reciprocated or oscillated toward the welding torch 16without the use of a bi-directional motor.

FIG. 7 is a schematic of the reciprocating wire feed system 48,illustrating various components of the reciprocating wire feed system 48that may be included with any of the embodiments discussed above. In theillustrated embodiment, the reciprocating wire feed system 48 includesgears 250, a drive roll 252, an encoder 254, a sensor 256, and interfacecircuitry 258. The gears 250 may be any of the gears discussed above,such as gears 88, 90, 160, 162, 210, and so forth. Similarly, the driveroll 252 may be any of the drive rolls discussed above. The encoder 254is configured to monitor a rotation of the gears 250 and or the driveroll 252. Similarly, the sensor 256 may be a position sensor, rotationalsensor, or any other sensor configured to detect motion or a position ofone of the components of the reciprocating wire feed system 48, such asthe gears 250 or the drive roll 252. Based on the parameters detected bythe encoder 254 and/or the sensor 256, speed, and/or acceleration,and/or movement, and/or direction of the welding wire 42 may becalculated and monitored. Based on the detected movement, motion, ordirection the welding wire 42, a desired current may be supplied to thetorch 16 by the power supply 10. For example, the interface circuitry258 may be configured to communicate with the interface circuitry 28 ofthe power supply 10 to enable proper adjustment of the current suppliedto the torch 16. The adjustment may be made using feedback orfeedforward controller. The movement of the welding wire 42 and thecurrent output of the power supply 10 may be synchronized to optimizearc formation, reduce spatter, improved deposition, travel speed,reduced heat input and distortion, calm down or agitate weld puddle andoscillation, or otherwise improve the welding process.

FIG. 8 is an assembled perspective view of the reciprocating wire feedsystem 48, illustrating another embodiment of a planetary gear system300. The illustrated embodiment may be capable of higher frequencyoscillations due to a high gear ratio of the system 48. In operation, aninput shaft, pinion, and gear mechanism 302 rotate continuously in onedirection to drive the welding wire 42 in a forward and backward motion,with a net forward motion. In certain embodiments, the input shaft,pinion, and gear mechanism 302 may be geared and/or synchronized with aneccentric mechanism 304. In other words, one or more of the input shaft,pinion, and gear mechanism 302, eccentric mechanism 304, or othercomponent of the planetary gear system 300 may include gear teeth tosynchronize movement of the different components of the planetary gearsystem 300. For example, the input shaft and/or the gear may rotatedcontinuously in a single direction, and rotation of the input shaftand/or the gear may be translated into forward and backyard motion, witha net forward motion, of the welding wire 42 via the eccentricmechanism, the vertical restraint 224, and the horizontal restraint 228.

As mentioned above, present embodiments may be used with 100% CO₂ gaswelding with EN, EP, AC, and with solid and tubular wires. Theembodiments described above enable rapid wire reversals at a rate higherthan 100 Hz, e.g. at 150-250 Hz, to transfer liquid metal at the end offiller wire in a controlled manner so that the welding current duringshort entry and short exit are minimized.

While only certain features of the present disclosure have beenillustrated and described herein, many modifications and changes willoccur to those skilled in the art. It is, therefore, to be understoodthat the appended claims are intended to cover all such modificationsand changes as fall within the true spirit of the present disclosure.

1. A reciprocating welding wire feed system, comprising: a first driveroll comprising a first set of protrusions extending radially outwardfrom the first drive roll and configured to drive a welding wire in alinear first direction; and a second drive roll disposed adjacent to thefirst drive roll, wherein the second drive roll comprises a second setof protrusions extending radially outward from the second drive roll andconfigured to drive the welding wire in a linear second directionopposite the first linear direction; wherein the first drive roll andthe second drive rolls do not contact the welding wire simultaneously.2. The system of claim 1, wherein the first set of protrusions and thesecond set of protrusions are configured to alternatingly contact thewelding wire at different times during operation of the reciprocatingwelding wire feed system.
 3. The system of claim 1, wherein the firstset of protrusions is spaced equidistantly about a first circumferenceof the first drive roll, the second set of protrusions is spacedequidistantly about a second circumference of the second drive roll, andthe first and second sets of protrusions are out of phase relative toone another.
 4. The system of claim 1, wherein each protrusion of thefirst set of protrusions has a first arc length about a firstcircumference of the first drive roll, each protrusion of the second setof protrusions has a second arc length about a second circumference ofthe second drive roll, and the first arc length is greater than thesecond arc length.
 5. The system of claim 1, wherein the first driveroll is fixed to a first gear, the second drive roll is fixed to asecond gear, and the first and second gears are synchronized with oneanother.
 6. The system of claim 5, comprising a motor coupled to thefirst gear or the second gear and configured to drive the first gear orthe second gear, wherein the motor, when in operation, rotates in onlyone direction.
 7. The system of claim 1, wherein each protrusion of thefirst set of protrusions comprises a respective trough that extendscircumferentially through the respective protrusion and that isconfigured to engage with the welding wire, and each protrusion of thesecond set of protrusions comprises a respective trough that extendscircumferentially through the respective protrusion and that isconfigured to engage with the welding wire.
 8. The system of claim 1,comprising a first idler roller disposed opposite the first drive rollrelative to the welding wire, and a second idler roller disposedopposite the second drive roll relative to the welding wire, wherein thefirst set of protrusions and the first idler roll are configured tointermittently capture and drive the welding wire in the first lineardirection, and the second set of protrusions and the second idler rollerare configured to intermittently capture and drive the welding wire inthe second linear direction.
 9. The system of claim 1, comprising athird drive roll disposed opposite the first drive roll relative to thewelding wire, and a fourth drive roll disposed opposite the second driveroll relative to the welding wire, wherein the first set of protrusionsand the third drive roll are configured to intermittently capture anddrive the welding wire in the first linear direction, and the second setof protrusions and the fourth drive roll are configured tointermittently capture and drive the welding wire in the second lineardirection.
 10. The system of claim 1, wherein the system is configuredto perform a gas metal arc welding, flux-cored arc welding, submergedarc welding, hot wire/cold wire tungsten inert gas welding, laserwelding, plasma welding, cladding, brazing process, a multi-wireprocess, or any combination thereof.
 11. A reciprocating welding wirefeed system, comprising: a first drive roll configured to contact awelding wire; a second drive roll disposed adjacent to the first driveroll on a same side of the welding wire, wherein the second drive rollis configured to contact the welding wire, a first expandable rolldisposed opposite the first drive roll relative to the welding wire; anda second expandable roll disposed opposite the second drive rollrelative to the welding wire; wherein the first expandable roll isconfigured to expand radially upon application of an electrical signalto the first expandable roll, and the second expandable roll isconfigured to expand radially upon application of the electrical signalto the second expandable roll.
 12. The system of claim 11, wherein thefirst expandable roll is configured to contract radially upon suspensionof the application of the electrical signal, and the second expandableroll is configured to contract radially upon suspension of theapplication of the electrical signal.
 13. The system of claim 11,wherein the first and second expandable rolls each comprise apiezoelectric crystal material, a ceramic material, or a combinationthereof.
 14. The system of claim 11, comprising an electrical systemconfigured to apply the electrical signal to the first expandable rollwhile suspending application of the electrical signal to the secondexpandable roll, and configured to apply the electrical signal to thesecond expandable roll while suspending application of the electricalsignal to the first expandable roll.
 15. The system of claim 11, whereinthe first drive roll, when in operation, is configured to drive thewelding wire in a first direction, and wherein the second drive roll,when in operation, is configured to drive the welding wire in a seconddirection opposite the first direction.
 16. The system of claim 11,wherein the first drive roll is fixed to a first gear, the second driveroll is fixed to a second gear, and the first and second gears aresynchronized with one another.
 17. The system of claim 16, comprising amotor coupled to the first gear, the second gear, or both and configuredto drive the first gear, the second gear, or both, wherein the motor,when in operation, is configured to rotate only in one direction duringoperation of reciprocating welding wire feed system.
 18. A method,comprising: driving rotation of a gear of a reciprocating welding wirefeed system with a motor rotating in only one rotational direction;feeding a welding wire through the reciprocating welding wire feedsystem in a first linear direction by driving the gear in the onerotational direction; and retracting the welding wire through thereciprocating welding wire feed system in a second linear directionopposite the first linear direction by driving the gear in the onerotational direction.
 19. The method of claim 18, wherein the gearcomprises a planetary gear disposed within a ring gear.
 20. The methodof claim 19, comprising: driving rotation of the planetary gear withinthe ring gear in the one rotational direction; transferring a firstlinear motion of the planetary gear to the welding wire to feed thewelding wire in the first linear direction; and transferring a secondlinear motion of the planetary gear to the welding wire to retract thewelding wire in the second linear direction.
 21. The method of claim 18,comprising driving rotation of a first drive roll having a first set ofprotrusions configured to contact the welding wire with the motor, anddriving rotation of a second drive roll having a second set ofprotrusions configured to contact the welding wire with the motor,wherein the first and second sets of protrusions are out of phase withone another.
 22. The method of claim 18, comprising: applying anelectrical signal to a first expandable roll to radially expand thefirst expandable roll such that the first expandable roll captures thewelding wire with a first drive roll to feed the welding wire in thefirst linear direction; suspending application of the electrical signalto the first expandable roll to radially contract the first expandableroll such that the first expandable roll disengages from the weldingwire and the first drive roll; and applying the electrical signal to asecond expandable roll to radially expand the second expandable rollsuch that the second expandable roll captures the welding wire with asecond drive roll to retract the welding wire in the second lineardirection.
 23. A consumable filler metal delivery system, comprising: areciprocating wire feeding gear assembly configured to move a wireforward and backward with a net forward motion; and a motor configuredto drive the reciprocating wire feeding gear assembly, wherein the motoris configured to rotate only in one direction during operation of theconsumable filler metal delivery system.
 24. The system of claim 23,wherein the system is configured to perform a gas metal arc welding,flux-cored arc welding, submerged arc welding, hot wire/cold wiretungsten inert gas welding, laser welding, plasma welding, cladding,brazing process, a multi-wire process, or any combination thereof. 25.The system of claim 23, comprising a wire feeder, wherein thereciprocating wire feeding gear assembly and the motor are disposedwithin the wire feeder.
 26. The system of claim 23, comprising a weldingtorch, wherein the reciprocating wire feeding gear assembly and themotor are disposed within the welding torch.
 27. The system of claim 23,wherein operation of the reciprocating wire feeding gear assembly issynchronized with a welding current waveform of the system.
 28. Thesystem of claim 23, wherein the reciprocating wire feeding gear assemblycomprises piezoelectric actuators configured to move the wire forwardand backward with the net forward motion.
 29. The system of claim 23,wherein the reciprocating wire feeding gear assembly comprises: a firstdrive roll comprising a first set of protrusions extending radiallyoutward from the first drive roll and configured to drive the wireforward; and a second drive roll comprising a second set of protrusionsextending radially outward from the second drive roll and configured todrive the wire backward.
 30. The system of claim 29, wherein the firstand second drive rolls are configured to rotate in the same direction.